Although most frequently, electrical devices (often intelligent devices equipped with computing capability) may communicate to each other using either wireless communication methods, or by electrical impulses such as electrical impulses sent over electrically conducting wire, or by optical methods (e.g. optical fiber communications methods), other methods of communication are also possible.
For example Willins, in U.S. Pat. No. 7,561,492 taught a system and method for using an ultrasonic wave transmitter to send information along a surface to an ultrasonic wave receiver. Other methods, such as sonic television remote controls, and the like are also known in the art.
As will be discussed, going forward in this invention, certain vibration mediated methods will be proposed to facilitate communication between various types of electrical devices. Often these electrical devices will themselves be equipped with microprocessors, microcontrollers, or other type of data processing capability. To help give specificity to this discussion, much of the disclosure will focus on the problems of communicating between photovoltaic type electrical devices. Thus a brief review of prior art photovoltaic array technology, particularly with regards to photovoltaic array communications technology, is in order.
As the costs of production of photovoltaic solar cells (also called photovoltaic panels, photovoltaic cells, solar photovoltaics, photovoltaics, PVs, solar cells and solar panels) have decreased, and as the costs for fossil fuel energy have increased, photovoltaic panels, and arrays of photovoltaic panels, have become an increasingly cost competitive method for generating electricity. Indeed, photovoltaic arrays are now one of the world's fastest growing sources of alternative energy. Thus methods of optimizing electrical energy produced by photovoltaic arrays are of large economic interest.
Photovoltaic solar cells normally operate by a process in which photons from sunlight interact with a solid state photovoltaic material, normally some sort of photodiode, and knock the electrons into a higher energy state. These electrons are then collected, and produce a DC electrical current that can be harnessed to do useful work. By combining a large number of individual photovoltaic solar cell panels into series and parallel circuits, these arrays can produce a substantial amount of DC electrical power, on the order of megawatts and more.
Since most electrical appliances are configured to use AC current at a fixed voltage, such as 115 or 230 volts, the DC electrical output from photovoltaic arrays is usually converted to an AC power output, often using an inverter. Typically inverters can adapt to a range of input DC voltages and currents, and produce AC power (at varying current levels) at a constant AC voltage. Although inverters convert DC energy to AC energy at a high efficiency, due to conservation of energy principles, the AC output power of an inverter will, of course, never exceed the DC input power to the inverter.
Photovoltaic cells work at their highest efficiency when they are pointed directly at the sun. As the amount of incident sunlight onto the photovoltaic cell becomes less favorable, the amount of solar energy or “irradiance” per square meter of the photovoltaic cell drops, and the number of photons knocking electrons to a higher energy state also drops. Although each photon will itself still have the same amount of energy, due to the lower amount of light, the number of energized electrons will drop, and thus the electrical current produced by the photovoltaic solar cell will also drop.
Many things can contribute to diminished solar irradiance. Due to the angle of the sun in the sky, the angle of the sun relative to the solar panel will generally be less favorable during the early morning and late afternoon. Clouds, shadows, and dirt on the solar panels can also contribute to diminished solar irradiance.
Each solar panel will operate at a maximum power output when subjected to the appropriate electrical load. Due to the internal resistance of the solar panel, and other factors, the electrical load that produces a maximum solar panel power output is not a constant load, but rather varies according to both the amount of current output by the solar panel, and the temperature that the solar panel is operating at.
Prior art solar power optimization circuits, exemplified by Chetty, U.S. Pat. No. 4,604,567, and Watkinson, U.S. Pat. No. 5,001,415; disclosed methods to optimize solar panel output power under varying conditions by briefly sampling the open circuit voltage of the solar panel array, and then varying the load on the solar panel (Chetty), or alternatively using a switching power converter to maximize power output (Watkinson). These power optimization units go by a number of different names, including variable load adjusters, power optimizer circuits, maximum power point tracker devices, and MPPT devices.
Although such prior art circuits can help improve the efficiency of individual solar panels and smaller solar panel arrays, the complexity of the problem as the size (e.g. number of individual panels) of the solar panel array increases should be appreciated.
Due to the nature of series and parallel electrical circuits, the maximum current through a series circuit is always limited by the maximum current that passes through the series circuit's weakest (highest resistance) link. Indeed if one element in a series circuit breaks, the whole circuit goes down. By contrast, due to the nature of parallel electrical circuits, the maximum current produced by a parallel circuit limited by the current generating capacity of the individual parallel circuit members.
Thus in a larger array of solar panels, even if the individual panels in the array are each equipped with prior art power optimization circuits, the array as a whole may still operate at suboptimal efficiency. For example, if one portion of the overall array is shadowed or obscured, the power optimization circuits controlling the obscured portion of the array may appropriately place a higher load on those solar panels, producing a correct local power optimization, but producing a suboptimal overall power optimization since these obscured panels may be connected in series or parallel circuits with other non obscured panels, and thus interfere with the power generation of the larger array as a whole.
Thus methods to enhance coordination between individual power optimization units and optimize overall array power production are of high commercial interest.